1. Field of the Invention
The present invention generally relates to transporting dollys for sheet material and, more particularly, is concerned with an improved wheel-supported carrier device for transporting sheet material on edge.
2. Description of the Prior Art
Workers installing sheets of drywall at construction sites, such as new houses, are ordinarily compensated on a piece basis. This means that in exchange for their labor, workers are paid a set price for each sheet of drywall installed. Thus, the highest compensation is earned by those workers who are able to install the highest numbers of sheets of drywall in a given period of time. As a result, speed of installation is a major concern to workers installing drywall.
Typically drywall sheet sizes are 4.times.8, 4.times.10, 4.times.12 and 4.times.16 width times length in feet and thicknesses of either one-half or five-eights inch. After being unloaded at the construction site, the sheets of drywall must be manually carried through doorways, along hallways, and up stairways to reach the place of installation. A single sheet of drywall of the aforementioned sizes weighs from 100-150 pounds. Thus, it is difficult for a single worker to maneuver the sheet without causing some damage to it. Typically, the worker has to drag or push the sheet of drywall over the floor and around corners of the inside framework of the house. This causes damage to the corners of the drywall sheet. Damage to sheets of drywall necessitates repair which increases cost.
Many different dollys and carriers have been proposed in the prior patent art for transporting sheet material. Representative examples of the prior art devices are the ones disclosed in U.S. Pat. No. 2,291,474 (Kalmbach), U.S. Pat. No. 3,090,635 (Masterson, Jr.,) U.S. Pat. No. 3,306,624 (Goss), U.S. Pat. No. 3,580,601 (Miles), U.S. Pat. No. 3,698,577 (Dean), U.S. Pat. No. 4,488,733 (Hellsten), U.S. Pat. No. 4,630,838 (Stockton) and U.S. Pat. No. 4,793,624 (Mace). Except for the dolly disclosed in the Masterson patent, the devices of these prior art patents appear to be too complicated, bulky and large to provide a satisfactory solution to the problem of the difficulty in handling heavy sheets of drywall at construction sites. Even the design of the Masterson dolly has certain shortcomings which make it much less than an optimum solution.
First, the Masterson dolly includes an elongated bed supported by a pair of wheels mounted for rotation in a fixed direction along opposite sides of the bed by a transverse axle. The wheels are thus mounted solely to rotate about a common transverse axis and not to swivel about vertical axes. This manner of mounting the wheels makes it difficult to maneuver around corners.
Second, the elongated bed of the Masterson dolly has a top longitudinal recess of concave cross-sectional shape which receives and supports the sheet of material on edge. A bed of this shape will provide inadequate lateral confinement of the lower edge of the sheet and thereby fail to prevent the sheet from inadvertently being pulled or pushed off the dolly from time to time, particularly while maneuvering the sheet and dolly around corners.
Consequently, a need still exists for improvements in devices for transporting sheet material, such as drywall, about construction sites so as to reduce the incidence of damage to the drywall and the difficulty of the overall installation process.